The Atlantic sturgeon (''Acipenser oxyrinchus'') is a large species of

sturgeon Sturgeon (from Old English ultimately from Proto-Indo-European language, Proto-Indo-European *''str̥(Hx)yón''-) is the common name for the 27 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the ...

native to both sides of the

Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...

, and associated river basins. It is a member of the family

Acipenseridae Sturgeon (from Old English ultimately from Proto-Indo-European language, Proto-Indo-European *''str̥(Hx)yón''-) is the common name for the 27 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the ...

, and, along with other sturgeon, it is sometimes considered a

living fossil A living fossil is a Deprecation, deprecated term for an extant taxon that phenotypically resembles related species known only from the fossil record. To be considered a living fossil, the fossil species must be old relative to the time of or ...

. The main range of the Atlantic sturgeon is in eastern North America, extending from

New Brunswick New Brunswick is a Provinces and Territories of Canada, province of Canada, bordering Quebec to the north, Nova Scotia to the east, the Gulf of Saint Lawrence to the northeast, the Bay of Fundy to the southeast, and the U.S. state of Maine to ...

, Canada, to the eastern coast of

Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...

, United States. A highly endangered disjunct population occurs in the

Baltic region The Baltic Sea Region, alternatively the Baltic Rim countries (or simply the Baltic Rim), and the Baltic Sea countries/states, refers to the general area surrounding the Baltic Sea, including parts of Northern, Central and Eastern Europe. Un ...

of Europe (today only through a reintroduction project). The Atlantic sturgeon was in great abundance when the first European settlers came to North America, but has since declined due to

overfishing Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing Fish stocks, fish stock), resu ...

water pollution Water pollution (or aquatic pollution) is the contamination of Body of water, water bodies, with a negative impact on their uses. It is usually a result of human activities. Water bodies include lakes, rivers, oceans, aquifers, reservoirs and ...

, and habitat impediments such as dams. It is considered threatened, endangered, and even locally extinct in many of its original

habitat In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...

s. The fish can reach 60 years of age, in length and over in weight.

Taxonomy

Alongside its relative the European sea sturgeon (''A. sturio''), the Atlantic sturgeon is one of the most basal members of the sturgeon lineage. The Gulf sturgeon (''A. desotoi''),

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

Gulf of Mexico The Gulf of Mexico () is an oceanic basin and a marginal sea of the Atlantic Ocean, mostly surrounded by the North American continent. It is bounded on the northeast, north, and northwest by the Gulf Coast of the United States; on the southw ...

-draining rivers in the southeastern United States, was formerly considered a subspecies of the Atlantic sturgeon. However, phylogenetic studies suggest that both have sufficient genetic divergence to qualify as distinct species. The two species appear to have diverged during the

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

Baltic population

The now nearly extinct sturgeon population in the

Baltic Sea The Baltic Sea is an arm of the Atlantic Ocean that is enclosed by the countries of Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden, and the North European Plain, North and Central European Plain regions. It is the ...

area belongs to the Atlantic sturgeon ''A. oxyrinchus'' rather than to the European species '' A. sturio'' as had been thought. ''A. oxyrinchus'' migrated to the Baltic about 1300 years ago and displaced the native ''A. sturio''. The last known specimen of the Atlantic sturgeon in the Baltic region was caught in 1996 near Muhumaa in

Estonia Estonia, officially the Republic of Estonia, is a country in Northern Europe. It is bordered to the north by the Gulf of Finland across from Finland, to the west by the Baltic Sea across from Sweden, to the south by Latvia, and to the east by Ru ...

. It was long, weighed , and was estimated to be about 50 years old.

Physical appearance

Rather than having true scales, the Atlantic sturgeon has five rows of bony plates known as

scutes A scute () or scutum (Latin: ''scutum''; plural: ''scuta'' "shield") is a bony external plate or scale overlaid with horn, as on the shell of a turtle, the skin of crocodilians, and the feet of birds. The term is also used to describe the anterio ...

. Specimens weighing over 800 lb and nearly 15 ft in length have been recorded, but they typically grow to be and no more than . Its coloration ranges from bluish-black and olive green on its back to white on its underside. It has a longer snout than other sturgeons and has four

barbel Barbel may refer to: *Barbel (anatomy), a whisker-like organ near the mouth found in some fish (notably catfish, loaches and cyprinids) and turtles *Barbel (fish), a common name for certain species of fish **''Barbus barbus'', a species of cyprini ...

s at the side of its mouth.

Behavior

Sturgeon are an

anadromous Fish migration is mass relocation by fish from one area or body of water to another. Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousa ...

species that live solitarily or in small groups. They migrate upriver in the spring to spawn. Sturgeons tend to inhabit the shallow waters of coastal shelves, coastal and estuarine areas on soft bottom in the sea, and can live down to a depth of . Adults are migratory while at sea and will make long migrations to coastal areas, while juveniles will stay in fresh or

brackish water Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuary ...

until they are between two and five years of age. However, many

larvae A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect developmental biology, development such as insects, some arachnids, amphibians, or cnidarians typical ...

and juveniles do start to migrate and disperse small distances from their spawning sites. Sturgeons are most generally known for feeding on crustaceans, worms, and molluscs. Sturgeons may have dominance hierarchies with large fish being dominant when competing for limited foraging space.

Life cycle

Atlantic sturgeon under six years of age stay in the

brackish Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuari ...

water where they were born before moving into the ocean. They may be long at this stage. In areas where

shortnose sturgeon The shortnose sturgeon (''Huso brevirostrum'') is a small and endangered species of North American sturgeon. As with most sturgeons, it is an anadromous bottom-feeder, which migrates upstream to spawn but spends most of its life feeding in rive ...

are also present, the adults of that species can be, and historically were for centuries, confused with immature Atlantic sturgeon. When mature, they travel upstream to spawn. The females may lay 800,000 to 3.75 million eggs in a single year, doing so every two to six years. After laying their eggs, females travel back downstream, but males may remain upstream after spawning until forced to return downstream by the increasingly cold water. They may even return to the ocean, where they stay near the

coastline A coast (coastline, shoreline, seashore) is the land next to the sea or the line that forms the boundary between the land and the ocean or a lake. Coasts are influenced by the topography of the surrounding landscape and by aquatic erosion, su ...

. The species is also known for its occasional 'leaping' behavior, during which the fish will emerge completely out of the water in a forceful motion that can be hazardous to anything unlucky enough to be struck. The exact reason why sturgeon leap remains unknown, although some scholars believe leaping is a form of group communication.

Threats

Sturgeons are widely distributed along the Atlantic coast of the United States. Their wide distribution and tendency to disperse has led to numerous subpopulations of sturgeon. This species is recorded to be Vulnerable and at risk of becoming an endangered species due to dam construction, dredging, dredge spoil disposal, groundwater extraction, irrigation, flow alterations, and other surface water withdrawals.

Harvest

Originally, the Atlantic sturgeon was considered a worthless fish. Its rough skin would often rip nets, keeping fishermen from catching more profitable fish. Sturgeon were one of the types of fish harvested at the first North American commercial fishery, and were the first cash "crop" harvested in

Jamestown, Virginia The Jamestown settlement in the Colony of Virginia was the first permanent British colonization of the Americas, English settlement in the Americas. It was located on the northeast bank of the James River, about southwest of present-day Willia ...

. Other fisheries along the Atlantic coast harvested them for use as food, a leather material used in clothing and bookbinding, and

isinglass Isinglass ( ) is a form of collagen obtained from the dried swim bladders of fish. The English word origin is from the obsolete Dutch ''huizenblaas'' – ''huizen'' is a kind of sturgeon, and ''blaas'' is a bladder, or German ''Hausenblase'', ...

, a gelatinous substance used in clarifying jellies, glues, wines and beer. However, the primary reason for catching sturgeon was the high-quality caviar that could be made cheaply from its eggs, called black gold by watermen. In the late 19th century, seven million pounds of sturgeon meat were exported from the US per year. Within years, however, that amount dropped to 22,000 pounds. The number later rose to about 200,000 pounds a year in the 1950s.

Susceptibility to anthropogenic disturbances

There are many wide-ranging subspecies along the Atlantic Coast of North America. Identification of distinct population segments (DPS) is problematic because of sturgeons' ability to disperse so widely. However, it is possible to do some characterization of genetic differentiation and estimate

gene flow In population genetics, gene flow (also known as migration and allele flow) is the transfer of genetic variation, genetic material from one population to another. If the rate of gene flow is high enough, then two populations will have equivalent ...

. This method has been used to determine possibility for listing under the U.S.

Endangered Species Act The Endangered Species Act of 1973 (ESA; 16 U.S.C. § 1531 et seq.) is the primary law in the United States for protecting and conserving imperiled species. Designed to protect critically imperiled species from extinction as a "consequence of e ...

. The sturgeon's characteristics and life history make it susceptible to anthropogenic disturbances and make population restoration particularly difficult. They have late

sexual maturity Sexual maturity is the capability of an organism to reproduce. In humans, it is related to both puberty and adulthood. ''Puberty'' is the biological process of sexual maturation, while ''adulthood'', the condition of being socially recognized ...

, only moderate

fecundity Fecundity is defined in two ways; in human demography, it is the potential for reproduction of a recorded population as opposed to a sole organism, while in population biology, it is considered similar to fertility, the capability to produc ...

, and spawn at low frequencies. Females spawn once every three to five years, and males every one to five years. This is due to their ability to live for an extremely long time (various sub-species can have a lifespan ranging from ten years to sixty years). The population of Atlantic sturgeons has decreased dramatically due to

overharvesting Overexploitation, also called overharvesting or ecological overshoot, refers to harvesting a renewable resource to the point of diminishing returns. Continued overexploitation can lead to the destruction of the resource, as it will be unable to ...

. The late 19th century saw a surge in demand for caviar, which led to overfishing of the Atlantic sturgeon. Today, only 22 out of its 38 original spawning rivers still have viable populations of the species. They are particularly susceptible to bycatch mortality due to the many fisheries that exist within their natal estuaries. Their habitat range, which usually includes coastal spawning sites and coastal migrations, makes sturgeon well within contact of coastal fisheries.

Effects of hypoxia

Hypoxia combined with high water temperatures in the summer has been shown to be consistent with decreased survival rates of young of the year sturgeon in Chesapeake Bay. Hypoxia is defined as low ambient oxygen levels, which may be very harmful to organisms living in the hypoxic body of water. Often, lower regions of the water column will be more hypoxic than upper levels, closer to the surface. When surface access is denied, the situation is lethal to sturgeon. Increased incidences of summertime hypoxia have led, in part, to degradation of many sturgeon nursery habitats in the United States.

Conservation status

In February 2012, the Atlantic sturgeon was listed by the National Oceanic and Atmospheric Administration Fisheries Service under the

(ESA). Four

distinct population segment {{no footnotes, date=February 2018 A distinct population segment (DPS) is the smallest division of a taxonomic species permitted to be protected under the U.S. Endangered Species Act. ''Species'', as defined in the Act for listing purposes, is a ...

s (DPSs) were listed as endangered (New York Bight, Chesapeake Bay, Carolina, and South Atlantic) while one DPS was listed as threatened (Gulf of Maine).NMFS. ''Endangered and Threatened Wildlife and Plants; Final Listing Determinations for Two Distinct Population Segments of Atlantic Sturgeon (Acipenser oxyrinchus oxyrinchus) in the Southeast''.''Federal Register;; v77, (February 6, 2012), 5914–5982.'' There are concerns that the construction of the bridge to replace the Tappan Zee connecting Rockland County to Westchester County in New York, in the Hudson River, may impact the sturgeon's

ecological stability In ecology, an ecosystem is said to possess ecological stability (or equilibrium) if it is capable of returning to its equilibrium state after a perturbation (a capacity known as Ecological resilience, resilience) or does not experience unexpecte ...

in the region."Group Petitions to Save a Prehistoric Fish From Modern Construction"
article by Lisa W. Foderaro in ''The New York Times'' July 21, 2015 The American Fisheries Society considers the fish as threatened throughout its entire range, although it is believed to no longer inhabit the full range it once did. In the Chesapeake watershed, the James River in Virginia is one of the last confirmed holdouts for that region's population. In May 2007, a survey captured 175 sturgeon in the river, with 15 specimens exceeding . A bounty-based survey of live Atlantic sturgeon in Maryland's portion of the bay found a high number of captures reported in 2005–06. In 2016, the

National Marine Fisheries Service The National Marine Fisheries Service (NMFS), informally known as NOAA Fisheries, is a United States federal agency within the U.S. Department of Commerce's National Oceanic and Atmospheric Administration (NOAA) that is responsible for the ste ...

considered designating sixteen rivers as endangered habitat, which would require more attention to be given to uses of the rivers that affect the fish. Then in 2018, NMFS actually mapped a total of thirty-one critical river habitats along the United States' Atlantic shores. Populations have declined dramatically over the last centuries, and even became extinct in Baltic range states in the later 20th century. Channelisation and barriers were part of the causes for declines affecting migration, along with pollution. Since 1996 Baltic sturgeon recovery has been attempted, with American donor populations used due to genetic similarities. Re-introduction with focus on returning these sturgeon to their native spawning grounds.

NatureServe NatureServe, Inc. is a non-profit organization based in Arlington County, Virginia, United States, US, that provides proprietary wildlife conservation-related data, tools, and services to private and government clients, partner organizations, and ...

considers the species ''Vulnerable''. A German-Polish project was underway in 2009 to reintroduce the sturgeon into the Baltic by releasing specimens caught in the Canadian Saint John River into the

Oder The Oder ( ; Czech and ) is a river in Central Europe. It is Poland's second-longest river and third-longest within its borders after the Vistula and its largest tributary the Warta. The Oder rises in the Czech Republic and flows through wes ...

, a river at the border between Germany and Poland where the species once spawned. The project expanded in 2013 to include Estonia, where one-year-old juveniles were released into the

Narva River The Narva, formerly also Narwa or Narova, flows north into the Baltic Sea and is the largest Estonian river by discharge. A similar length of land far to the south, together with it and a much longer intermediate lake, Lake Peipus, all togeth ...

. The Baltic sturgeon population is considered

Critically Endangered An IUCN Red List critically endangered (CR or sometimes CE) species is one that has been categorized by the International Union for Conservation of Nature as facing an extremely high risk of extinction in the wild. As of December 2023, of t ...

by the

IUCN The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the status ...

. In 2012, the Atlantic sturgeon received protection under the Endangered Species Act.

Conservation designation

IUCN: Vulnerable CITES: Appendix II The American Fisheries Society considers it endangered in all stream systems except conservation-dependent in the Hudson, Delaware, and Altamaha Rivers. The Atlantic sturgeon of the

Delaware River The Delaware River is a major river in the Mid-Atlantic region of the United States and is the longest free-flowing (undammed) river in the Eastern United States. From the meeting of its branches in Hancock, New York, the river flows for a ...

are listed under the ESA as part of the New York Bight

(DPS), which includes all Atlantic sturgeon that spawn in watersheds draining to coastal waters from Chatham, Massachusetts, to the Delaware-Maryland border on Fenwick Island, the Chesapeake Bay DPS, the Carolina DPS and the South Atlantic DPS, while the Gulf of Maine DPS is listed threatened. Canadian-origin populations are not currently listed under the U.S. ESA. NMFS believes fewer than 300 spawning adults are in the Delaware River population; just over 100 years ago the estimated population was 180,000 spawning adult females.

Management

Atlantic sturgeon are now a threatened species. Management of the species is largely based on the restriction of fishing of the species. This helps limit fishing mortalities of sturgeon to bycatch.

External links

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